The fluid catalyst cracking or “FCC” process has been extensively relied upon for the conversion of starting materials, such as vacuum gas oils and other relatively heavy oils, into lighter and more valuable products. In an FCC reaction zone, the starting material, whether it be vacuum gas oil or another oil, is contacted with a finely particulated, solid catalytic material that behaves as a fluid when mixed with a gas or vapor. This catalytic material possesses the ability to catalyze the cracking reaction. During the cracking reaction, coke is deposited on the surface of the catalyst as a by-product of the cracking reaction. Coke includes hydrogen, carbon, and other material such as sulfur, and it interferes with the catalytic activity of FCC catalysts.
Facilities for the removal of coke from FCC catalyst, so-called regeneration facilities or “regenerators”, are ordinarily provided within an FCC unit. Typically, coke-contaminated catalyst enters the regenerator and is contacted with an oxygen containing gas at conditions such that the coke is oxidized. A flue gas, which includes excess regeneration gas and the gaseous products of coke oxidation, as well as solid particulate matter that is removed from the catalyst during regeneration and commonly referred to as “catalyst fines,” leaves the regenerator by a flue vent that is located at the top of the regenerator. The fluidized catalyst is continuously circulated from the reaction zone to the regeneration zone and then again to the reaction zone. Catalyst exiting the reaction zone is referred to as being “spent”, that is partially deactivated by the deposition of coke upon the catalyst. Catalyst from which coke has been substantially removed is referred to as “regenerated” catalyst.
In recent years, some environmental control agencies have begun to place limits or “caps” on the amount of particulate matter that may be vented through the flue vent. In circumstances where it is found that the flue gas contains particulate matter at levels that exceed such caps, it is typically required to install one or more particulate removal systems, such as flue gas scrubbers, separators, electrostatic precipitators, and/or other filtering units, at the flue vent. The installation and operation of these particulate removal systems adds significant capital and operational expenses to the FCC process.
Accordingly, it is desirable to provide improved FCC processes. In addition, it is desirable to provide such processes that reduce the amount of particulate material contained within the FCC regenerator flue gas. Still further, it is desirable to provide such processes that do not require, or that reduce the need for, particulate removal systems installed at the flue vent. Furthermore, other desirable features and characteristics will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background.